|Publication number||US4394688 A|
|Application number||US 06/296,068|
|Publication date||Jul 19, 1983|
|Filing date||Aug 25, 1981|
|Priority date||Aug 25, 1981|
|Publication number||06296068, 296068, US 4394688 A, US 4394688A, US-A-4394688, US4394688 A, US4394688A|
|Inventors||Hitoshi Iida, Pay-Shin King|
|Original Assignee||Hamamatsu Systems, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (60), Classifications (7), Legal Events (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates generally to video systems and more particularly to a video system which includes an adjustable digital gamma correction which is used to selectively emphasize or enhance the contrast of a video picture over different regions of interest.
In a television system the relationship between the brightness of a portion of an object and the brightness of the corresponding portion of the image is generally expressed by the formula:
where y is the magnitude of the output signal, x is the magnitude of the input signal and γ is the power, referred to as the gamma, to which x must be raised to be equal to y. In order to determine the overall gamma of a television system, the gamma of the television camera and the gamma of the television monitor or receiver are multiplied together. In an ideal or distortionless system the overall gamma is 1.0. Unfortunately, in most all television cameras the gamma (which is determined by the composition of the photosensitive material in the vidicon) is between around 0.6 to 0.5 while in most all television monitors the gamma (which is determined by the composition of the phosphorescent material in the screen) is designed to be about 2.2. Consequently, the overall gamma is normally not equal to 1.0 and the contrast of the resulting image is somewhat distorted (i.e. in certain areas the contrast is greater than it should appear and in other areas the contrast is less than it should appear).
In order to correct for this distortion, a type of analog electrical circuit called a gamma correction circuit is normally incorporated into the system. The circuit provides a gamma which when multiplied together with the gamma of the television camera and the gamma of the television monitor produces an overall gamma in the system of around 1.0. These gamma correction circuits are normally built into the television camera or a control module for the television camera and are usually adjustable within a small range, such as from 0.85 to 1.0, to compensate for variations that may be present in the gamma of the particular vidicon tube used in the television camera. Once set to the particular value needed to produce an overall gamma of 1.0 (or as close to 1.0 as is possible), the gamma of the gamma correction circuit is generally not changed. However, in some closed circuit television systems used for surveillance purposes it is known to provide a knob or other manually adjustable means at the television monitor for adjusting the gamma produced by the gamma correction circuit for the purpose of intentionally distorting the contrast over areas of interest where the lighting is poor and the resulting image difficult to perceive. The amount of intentional distortion that can be produced, however, is limited to the small range of adjustability in the analog gamma correction circuit.
It is known to intentionally distort the contrast of an image formed in video microscope systems used in industrial and research applications to examine characteristics and properties of very small objects in order to improve the visibility of the objects being examined by selectively manipulating the gain and offset knobs in the video camera and the diaphragm and compensator settings in the microscope. An example of this technique of contrast enhancement may be found in a publication entitled Video-Enhanced Contrast Polarization (AVEC-POL) Microscopy appearing in Cell Motility 1:275-289 (1981), Alan R. Liss, Inc.
It is also known to convert analog video signals into video data for temporary or permanent storage and/or digital signal image processing. One known type of digital signal image processing that is often performed to improve the quality of an image is noise reduction. An example of a known digital type image processing system may be found in U.S. Pat. No. 4,240,113, to Michael et al. Another example of a digital image processing system is described in Hamamatsu Systems Inc. Product Bulletin/2001 Rev. 2 2-81.
It is an object of this invention to provide a new and improved video system which is especially suited for use in, but not exclusively limited to, industrial and research applications.
It is another object of this invention to provide a novel method and system for selectively manipulating the contrast of a video image.
It is a further object of this invention to provide a video system having an adjustable digital gamma correction.
It is yet still another object of this invention to provide a novel method and system for selectively manipulating the contrast of a video image over low intensity areas.
It is a further object of this invention to provide a novel method and system for selectively manipulating the contrast of a video image over high intensity areas.
It is yet still another object of this invention to provide a video system in which the gamma is adjustable and useable over a range from 0.1 or lower to 3.0 or higher.
It is another object of this invention to provide a system and method for digitally adjusting the gamma of a video system in order to provide contrast enhancement in selected areas of interest.
A video system constructed according to the teachings of the present invention includes a television camera, a digital video signal processor coupled to the output of the television camera and a television monitor coupled to the output of the digital video signal processor. The digital video signal processor includes an analog to digital converter for converting analog video signals from the television camera into video data, a random access memory device through which the video data is passed and in which the video data is altered in accordance with the contents of a table-look-up temporarily written therein, a read only memory device containing a plurality of different table-look-ups for use in the random access memory device, each table-look-up containing data representing a different gamma correction, a central processing unit for obtaining a table-look-up from the read only memory device and then writing the table-look-up so obtained into the random access memory device in response to control signals applied thereto, a manually operated control device for applying control signals to the central processing unit for selecting which table-look-up is read out from the read only memory device and then written into the random access memory device and an analog to digital converter for converting the processed video data into analog video signals. In the operation of the digital video system, the contrast of the video picture appearing the television monitor is adjusted for optimum viewing conditions over an area of interest by changing the particular table-look-up in the random access memory device until the most favorable picture is produced.
The foregoing and other objects as well as many advantages of the invention will appear from the description to follow. In the description, reference is made to the accompanying drawings which form a part thereof, and in which is shown by way of illustrating, specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.
In the drawings wherein like reference numerals represent like parts, the sole FIGURE is a simplified block diagram of a video system including a digital video signal processor constructed according to the principles of the present invention.
Referring now to the drawings, there is illustrated in the sole FIGURE a simplified block diagram of a video system constructed according to the teachings of the present invention and identified generally by reference numeral 11.
Video system 11 includes a television camera 13 for generating analog video signals of an object or scene (or an optical image of an object or scene such as may be formed by a microscope), a digital video signal processor 15 for digitally processing the video signals obtained from the TV camera 13 and a television monitor 17 for displaying an image of the processed video signals.
The digital video signal processor 15 includes an analog to digital converter 19 for converting the analog video signals from TV camera 13 into video data. The video data from analog to digital converter 19 is transmitted to one of two inputs of a multiplexer 21 and to the input of a frame memory processor 23. The video data from analog to digital converter 19 may also be transmitted to a host or main computer (not shown) for permanent storage and processing, if desired.
In the frame memory processor 23, video data of a single frame is temporarily stored and processed either before or after storage. The frame memory processor 23 is shown in the FIGURE as including a pair or arithmetic logic units 25 and 27 and a frame memory 29. Frame memory processor 23 performs various known arithmetic type video signal processing functions, such as summing, averaging or differencing, the particular construction of frame memory processor 23 to perform these functions for purposes such as noise reduction not being considered a part of the invention and the particular components shown therein being for illustrative purposes only. Frame memory 29 may comprise a pair of Intel chips number 2117. An example of a known frame memory processor capable of performing adding, substracting and averaging type signal processing is described in the above referenced Hamamatsu Systems Inc. Product Bulletin/2001, Revision 2, 2/81. The output of the frame memory processor 23 is transmitted to the other input of multiplexer 21.
The video data from multiplexer 21, which is obtained either from analog to digital converter 19 or frame memory processor, is transmitted to a high speed random access memory device 31, where it is modified by a table-look-up which is temporarily written therein. Random access memory device 31 may comprise a pair of Fairchild chips number 93L422 and conventional associated logic circuitry. Random access memory device 31 is loaded with the table-look-up which is used to modify the video data from a central processing unit (CPU) 33 which controls the overall operations of the digital video signal processor 15 through signals sent over appropriate control lines (not shown). CPU 33 may be, for example, an Intel chip number 8080. The program for operating CPU 33 is stored in a memory (not shown) and instructions for executing the operating program are entered through a manually operated control panel 35 which includes a keyboard 37 and a joystick 39.
The table-look-up which is sent to random access memory device from CPU 33 is obtained from a bank of different table-look-ups permanently stored in a read only memory device 41 which is coupled to CPU 33. Each one of the table-look-ups in memory device 41 is for a different gamma correction. For example, there may be a bank of thirty table-look-ups, with each table-look-up having a different gamma correction, the smallest gamma correction table being 0.1 or smaller and the largest gamma correction table being 3.0 or larger. As can be appreciated, if the gamma resulting from TV camera 13 and TV monitor 17 is, for example, 1.32 a set of gamma correction tables having a range of 0.1 to 3.0 will enable the overall gamma to be changed from 0.132 to 3.966. Read only memory device 41 may comprise a pair of Intel chips number 2716 and associated logic circuitry.
The modified output data from random access memory device 31 is fed into a digital to analog converter 43 where it is converted into analog video signals. The modified output data may also be sent to the host computer, if desired. The image corresponding to the video output signals from digital to analog converter 43 is displayed on TV monitor 17.
In the operation of the digital video signal processor 15, the particular table-look-up that is read out from the read only memory device 41 and written into the random access memory is controlled through the manually operated control panel 35. For example, the CPU 33 may be programmed so that the specific table-look-up written into the random access memory 31 from the read only memory 41 is determined by the angular position of the joy stick 39. Alternatively CPU 33 may be programmed so that different look-up-tables can be moved from read only memory 41 to random access memory 31 by depressing different keys or combinations of keys on the keyboard 37. As can be appreciated, the gamma correction applied to the video data can thus be very easily and very quickly changed over a range limited solely the number of different tables stored in the read only memory device 41 and the gamma values preselected for the individual tables.
In using the digital video signal processor 15 to manipulate contrast, data sent to multiplexer 21 either directly from analog to digital converter 19 or from frame memory processor 23 is fed from multiplexer 21 into random access memory 31, the particular data selected being controlled by CPU 33. The gamma correction table inserted into random access memory device 31 is than changed until the most favorable image is formed on the screen of the TV monitor 17. By changing the gamma correction over a portion of or over the entire range of table-look-ups, areas of interest in the resulting picture may be seen which might not otherwise be visually perceptible.
As is known, for certain applications such as viewing video pictures of X-rays, it is benefical to emphase contrast in low intensity areas while in other applications such as in video microscopy it is beneficial to emphasize contrast in high intensity areas. Thus, in certain instances low gamma corrections are desirable while in other instances high gamma corrections are desirable.
As is also known, at very high or very low gammas, noise represents a problem that can very adversely effect the resulting picture. However, by processing the video data through frame memory processor 23, the noise can be easily reduced or substantially eliminated. Therefore, when using very high or very low gammas, the video data should be processed for noise reduction in the frame memory processor 23.
The above description is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3800078 *||Dec 18, 1972||Mar 26, 1974||Ibm||Digitally compensated scanning system|
|US4148070 *||Jan 31, 1977||Apr 3, 1979||Micro Consultants Limited||Video processing system|
|US4242707 *||Aug 23, 1978||Dec 30, 1980||Chyron Corporation||Digital scene storage|
|US4335427 *||Apr 21, 1980||Jun 15, 1982||Technicare Corporation||Method of selecting a preferred difference image|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4568978 *||Jun 15, 1983||Feb 4, 1986||U.S. Philips Corporation||Method of a circuit arrangement for producing a gamma corrected video signal|
|US4639783 *||Nov 30, 1984||Jan 27, 1987||Rca Corporation||Video signal field/frame storage system|
|US4670788 *||Nov 8, 1985||Jun 2, 1987||Kabushiki Kaisha Toshiba||Gray scale transformation circuit|
|US4688095 *||Feb 7, 1986||Aug 18, 1987||Image Technology Incorporated||Programmable image-transformation system|
|US4740833 *||Jul 16, 1986||Apr 26, 1988||Fuji Photo Film Co., Ltd.||Apparatus for producing a hard copy of a color picture from a color video signal processed in accordance with a selected one of a plurality of groups of color conversion coefficients associated with different kinds of color separating filters|
|US4786968 *||Jul 16, 1987||Nov 22, 1988||Sony Corporation||Gamma correction of digital video data by calculating linearly interpolated gamma correction values|
|US4833532 *||Jun 8, 1987||May 23, 1989||Canon Kabushiki Kaisha||Color copier for making a positive color copy from a color negative film including means for indicating the type of film and means for removing the orange mask component of the indicated film from three color component signals used to make the copy|
|US4907288 *||Sep 16, 1987||Mar 6, 1990||Elscint Ltd.||Image contrast enhancement arrangement|
|US4931864 *||Sep 27, 1989||Jun 5, 1990||Canon Kabushiki Kaisha||Image forming apparatus which performs gamma correction on the basis of a cumulative frequency distribution produced from a histogram of image data representing a selected area of an image|
|US5006937 *||Jul 27, 1990||Apr 9, 1991||Canon Kabushiki Kaisha||Imaging data processing apparatus|
|US5196924 *||Jul 22, 1991||Mar 23, 1993||International Business Machines, Corporation||Look-up table based gamma and inverse gamma correction for high-resolution frame buffers|
|US5249056 *||Jul 16, 1991||Sep 28, 1993||Sony Corporation Of America||Apparatus for generating video signals from film|
|US5263099 *||Nov 17, 1989||Nov 16, 1993||Picker International, Inc.||High speed window and level function modification for real time video processing|
|US5453845 *||Apr 28, 1994||Sep 26, 1995||Canon Kabushiki Kaisha||Apparatus for providing variable gamma correction in both on-line and off-line modes of operation|
|US5548327 *||Jun 5, 1995||Aug 20, 1996||Sony Corporation||Apparatus for selectively generating and enhancing within a window of signal values, video signals representing photographic images previously recorded in a film on a photographic film-type medium|
|US5586236 *||Aug 11, 1993||Dec 17, 1996||Object Technology Licensing Corp.||Universal color look up table and method of generation|
|US5696850 *||Dec 21, 1995||Dec 9, 1997||Eastman Kodak Company||Automatic image sharpening in an electronic imaging system|
|US5796384 *||Dec 21, 1995||Aug 18, 1998||Samsung Electronics Co., Ltd.||Gamma correction circuit of a liquid crystal display using a memory device|
|US5963271 *||Jan 29, 1997||Oct 5, 1999||Canon Kabushkik Kaisha||Image processing apparatus and method with aperture correction|
|US6323515||Aug 24, 1998||Nov 27, 2001||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US6335716 *||Aug 31, 1998||Jan 1, 2002||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor display device correcting system and correcting method of semiconductor display device|
|US6577340||Jun 13, 1997||Jun 10, 2003||Sony Corporation||Apparatus for generating video signals representing a photographic image previously recorded in a frame on a photographic film-type medium|
|US6597014||Mar 31, 2000||Jul 22, 2003||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US6597034||Oct 4, 2001||Jul 22, 2003||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US6667494||Aug 11, 1998||Dec 23, 2003||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US6670635||Mar 31, 2000||Dec 30, 2003||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US6717179||Mar 31, 2000||Apr 6, 2004||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US6833876||Feb 16, 2000||Dec 21, 2004||Zilog, Inc.||Using a reduced memory look up table for gamma correction through interpolation|
|US6900499||Apr 28, 2003||May 31, 2005||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US7042523||Jun 30, 2003||May 9, 2006||Texas Instruments Incorporated||Video correction system and method using logarithmic conversion|
|US7126156||Nov 3, 2003||Oct 24, 2006||Semiconductor Energy Laboratory Co., Ltd.||Thin film transistor display device with integral control circuitry|
|US7221393 *||May 1, 2002||May 22, 2007||Sony Corporation||Color imaging device and method|
|US7426316 *||Apr 29, 2002||Sep 16, 2008||Nokia Corporation||Method and apparatus for image improvement|
|US7495278||May 16, 2005||Feb 24, 2009||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US7750347||Oct 19, 2006||Jul 6, 2010||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US8064716 *||Oct 25, 2006||Nov 22, 2011||Soundstarts, Inc.||Apparatus and methods for enhancing digital images|
|US8103123||Aug 7, 2008||Jan 24, 2012||Nokia Corporation||Method and apparatus for image improvement|
|US9053679||Sep 16, 2004||Jun 9, 2015||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor display device correcting system and correcting method of semiconductor display device|
|US20020122119 *||May 1, 2002||Sep 5, 2002||Sony Corporation||Color imaging device and method|
|US20030002749 *||Apr 29, 2002||Jan 2, 2003||Nokia Corporation, Espoo Finland||Method and apparatus for image improvement|
|US20040031986 *||Apr 28, 2003||Feb 19, 2004||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US20040094765 *||Nov 3, 2003||May 20, 2004||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US20040268201 *||Jun 30, 2003||Dec 30, 2004||Towfique Haider||Video correction system and method using logarithmic conversion|
|US20050041122 *||Sep 16, 2004||Feb 24, 2005||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor display device correcting system and correcting method of semiconductor display device|
|US20050218405 *||May 16, 2005||Oct 6, 2005||Semiconductor Energy Laboratory Co., Ltd.||Non-volatile memory and semiconductor device|
|US20060055664 *||Sep 13, 2004||Mar 16, 2006||Repetto Mark E||Unified user input device|
|US20070034873 *||Oct 19, 2006||Feb 15, 2007||Semiconductor Energy Laboratory Co., Ltd.||Semiconductor device and semiconductor display device|
|US20070104384 *||Oct 25, 2006||May 10, 2007||Rodney Shaw||Apparatus and Methods for Enhancing Digital Images|
|US20080303926 *||Aug 7, 2008||Dec 11, 2008||Nokia Corporation||Method and apparatus for image improvement|
|US20090040077 *||Sep 22, 2008||Feb 12, 2009||Repetto Mark E||Unified user input device|
|DE3441162A1 *||Nov 10, 1984||Jul 25, 1985||Elscint Ltd||Arrangement for improving the imaging contrast|
|EP0382100A1 *||Feb 1, 1990||Aug 16, 1990||Canon Kabushiki Kaisha||Gamma correction device|
|EP0434208A1 *||Nov 16, 1990||Jun 26, 1991||Picker International, Inc.||Imaging systems and methods|
|EP0574943A2 *||Jun 18, 1993||Dec 22, 1993||Matsushita Electric Industrial Co., Ltd.||Apparatus and method for limiting gain in a digital gamma corrector|
|EP0574943A3 *||Jun 18, 1993||Jun 1, 1994||Matsushita Electric Ind Co Ltd||Apparatus and method for limiting gain in a digital gamma corrector|
|EP0632406A1 *||Jun 29, 1994||Jan 4, 1995||Eastman Kodak Company||Real-time window/leveling on a radiographic workstation|
|EP0810778A2 *||Jun 2, 1997||Dec 3, 1997||SANYO ELECTRIC Co., Ltd.||Digital still camera with a gamma correction circuit|
|EP0810778A3 *||Jun 2, 1997||Mar 14, 2001||SANYO ELECTRIC Co., Ltd.||Digital still camera with a gamma correction circuit|
|EP0883103A1 *||Jun 5, 1997||Dec 9, 1998||THOMSON multimedia||Direct view liquid crystal display with automatic colour adjustment|
|WO2001016930A1 *||Apr 19, 2000||Mar 8, 2001||Siemens Aktiengesellschaft||Method and device for controlling a colour display with not more than one control element per pixel|
|U.S. Classification||348/28, 348/254, 382/254, 348/E05.074|
|Aug 25, 1981||AS||Assignment|
Owner name: HAMAMATSU SYSTEMS, INC., 332 SECOND AVENUE, WALTHA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:IIDA, HITOSHI;KING, PAY-SHIN;REEL/FRAME:003915/0968
Effective date: 19810821
|Feb 28, 1987||REMI||Maintenance fee reminder mailed|
|Jun 5, 1987||SULP||Surcharge for late payment|
|Jun 5, 1987||FPAY||Fee payment|
Year of fee payment: 4
|Feb 19, 1991||REMI||Maintenance fee reminder mailed|
|Jul 21, 1991||LAPS||Lapse for failure to pay maintenance fees|
|Oct 1, 1991||FP||Expired due to failure to pay maintenance fee|
Effective date: 19910721